Utica Oil Boiler Most Efficient Configuration Question

ForTheGlory

Hi all,

We just moved into a house that has a Utica Starfire 3 Oil Boiler feeding baseboard hot water heat. The boiler also provides hot water that is mixed before feeding to an electric hot water heater. I had the boiler serviced a few days ago after moving in, and the tech told me that he didn't think my system was configured in the most efficient way and he suggested a change.

The boiler has 4 zones with separate circulators. One zone is controlled by a Honeywell L8124 aquastat on the side of the boiler (set to 160 deg low, 180 deg high, 10 deg offset), and then there are 3 separate Honeywell RA89A relays on the wall for the other three zones. He pointed out that these relays are unable to call for heat and just start their separate circulators.

He then suggested replacing the relays with a 4 zone Taco relay board so that all zones would be able to call for heat and having the output of the relay board control the aquatstat, and then this would allow us to set the low point much lower (he suggested 110 deg, which looks like it is the lowest setting on the Aquastat; I don't recall if he suggested lowering the high point as well) and save significant fuel (especially in the summer when all the boiler is doing is providing preheated water to the electric hot water heater so anything over 120 is unnecessary; I asked about just turning the boiler off in the summer and he suggested against it saying it could cause leaks in the boiler).

I had another contractor out to get a second opinion the next day, and he said he understood where the first guy was coming from but wasn't sure that it would save us enough money to make it worth the costs of the work, he also wasn't sure that 110 deg was warm enough to prevent leaking. As a side note, he also pointed out that the boiler is probably oversized and would typically be intended for a house about twice the size of ours. Note that unlike the first person who was a service technician, this guy was a salesman.

Does anybody have any suggestions about what the best (best being most efficient and worth the cost of the changes) path is here (do what the first guy suggested, do nothing as the second guy was leaning towards, or some other solution)? Trying to learn as much as I can about the system as well, as I had a heat pump in my previous house so I am completely unfamiliar with boilers. Another piece of info that may be relevant is that I am also planning to replace the old school Honeywell T87 thermostats with Ecobee3 stats.

Thanks for any help anybody can provide!

ForTheGlory

Wow, this is some great info! Thanks so much. You really clarified the situation. I got a price from the second contractor which I thought was way too high but am still waiting for a price from the first one.

Just to make sure I am following everything correctly, it sounds like you are saying that year-round I should keep the boiler running such that the temp never gets down to 128F. Is this correct? If so, do you think it makes sense to keep using the boiler to preheat the domestic hot water or would it be better to just separate the domestic hot water from the boiler and use the electric hot water heater only?

ForTheGlory

Thanks for responding again!

Cost of electricity on our first bill was 10.5 cents per kilowatt hour.
Cost of oil on our first fill up was $1.999 per gallon.
Not quite sure how to estimate hot water usage. We are a 2 adult, 1 child household (will be 2 children later this year). At our old house, we used somewhere in the vicinity of 4000-5000 gallons per month (all water, not just hot).

Do you think the contractors' concerns about turning off the boiler in the summer leading to leaking are overblown?

ForTheGlory

Thank you very much for your help!

So to make sure I captured everything properly, your suggestion is to replace the relays so that they can all call for heat, set the low limit to 140F, and experiment to see how low I can get the high limit. You lean towards leaving the boiler on year round at that setting given my energy costs, but I could safely turn it off in the warm months if I wanted. Did I capture that correctly?

Do you have any suggestions about where to set the aquastat offset temp (currently 10F)?

Again, thanks so much. This has been an education!

Bob Bona_4

Good advice, I'd add ditching the current tankless coil arrangement and electric water heater, and installing an indirect water heater as a new zone. This way the boiler doesn't have to maintain temp all the time.

ForTheGlory

Hatterasguy,

Do you think the swap to an L7224 would result in significant fuel savings or would the change primarily result in less wear and tear on the boiler? I have noticed that the boiler only seems to run for a few minutes at at time.

ForTheGlory

Thanks for the help!

I am looking into installing the Taco SR504 myself because the prices I got from the contractors were just too high, and it doesn't look too hard, but I just want to make sure I get the wiring right. Does this link - https://www.taco-hvac.com/uploads/FileLibrary/SR504(102-084).pdf - show the proper way to wire the SR504 to the L8124 aquastat (for both tankless coil and cold start configurations)? I am thinking about changing the aquastat as well, but for the purposes of this discussion, I will leave it as is. Currently, the thermostat that can fire the boiler is connected to the T/T connections on the aqua stat, the aquastat is wired to the circulator for that thermostat's zone, and the ZC and ZR connections on the aquastat are unused. Am I correct that in the new configuration (for tankless coil), the aquastat's ZC and ZR terminals would be connected to the SR504 as shown in that PDF and the aquastat's thermostat and circulator terminals would no longer be used?

Also, can I safely use the old Honeywell thermostats with the Taco relay board R/W connections (they currently hook up to T/T terminals on the RA89As and Aquastat) as an interim step before installing my new ecobee3 thermostats? That way I can verify I hooked up the relay board correctly before proceeding with the thermostat change.

Paul48

I think this is better http://www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf
Pay attention to the warning about 2 power sources.

ForTheGlory

Paul48,

Thanks! I see the power source warning on page 3. Do you also mean the wiring diagram on the same page? If so, that diagram looks like it is even more complete, perfect!

Two questions-

I see they have a boiler circulator connection to the aquastat marked "if attached". I don't think I have a boiler circulator. Is there a good way to confirm this?

Second, it shows a thermostat hooked up to the aquastat. I thought all the thermostats would hook up to the SR504. Do I need to hook one of them up to the aquastat still?

Paul48

Don't you have 1 t-stat that fires the boiler and turns on a circ? Don't you have (as described), a circulator on boiler, or 1 currently controlled by the aquastat?.
Here's my unprofessional take on it. I know how the 8124 works. I don't understand their use of "ZC" and "ZR", but I trust they know what they are doing, and I would wire mine exactly like theirs.

ForTheGlory

Currently one thermostat is hooked up to the T/T connections on the aquastat and the circulator for that zone is hooked up to the C1/C2 connections on the aquastat. The aquastat is hooked up to the burner. The other three thermostats are hooked up to RA89As which are connected to their respective circulators (these three do not interact with the aquastat or burner at all). Are you saying I should leave one of the thermostat/circulator pairs on the aquastat as is and NOT move all four to the SR504?

I don't trust that the people who installed my system knew what they were doing since they have it configured so inefficiently and such that only one zone can fire the boiler.

Paul48

I'd leave one hooked to the aquastat, just as they show. That way, you are only dealing with the zones hooked to the RA89A relays. The bottom line is, you want all the zones to be able to call the boiler, and that will do that.

ForTheGlory

So, is there any reason I couldn't use an SR503 instead of an SR504 then?

Paul48

If it suits your needs...sure. I thought you already had the 504.

ForTheGlory

No, I haven't purchased the parts yet. I am trying to figure out what suits my needs! I was planning on having this done professionally but got two quotes both of which were about $1000 more than it would cost me to do myself.

Paul48

OK......It doesn't affect which SR you choose, but you need to know if your boiler has a low water cut-off. It's a safety device that shuts the burner down if the boiler leaks and prevents a dry fire. Notice on the left of the wiring diagram.You want to make sure it doesn't wind up getting defeated by your new wiring(if you have one). Just make sure you follow the wiring completely.

ForTheGlory

Thanks for the tip. I did notice that but forgot to ask about it. I will need to investigate.

On page 83 of the big PDF you linked to it shows a zoom in on the connection from the switching relay to aquastat. It mentions there that you only need the thermostat hooked up to the aquastat if it is an independent zone. Was your recommendation to leave that thermostat there purely to simplify the wiring work that needs done? Because I just thought of the fact that once I install my new ecobee3 thermostats they will need a common, which the L8124 doesn't provide, so I may need to move all 4 thermostats to the relay anyway for the common. Am I missing something here?

Paul48

That shows zone control connection. If you were using zone valves, not circulators. Contact Taco.......explain that you want to get all the stats and circs on a SR, but don't want to lose the circ control feature of the 8124. It may be the only form of boiler protection you have.

ForTheGlory

I will call Taco, but are you sure you aren't looking at page 80 (for zone control) and not page 83 (for switching relays)? What kind of boiler protection are you referring to?

ForTheGlory

Hatterasguy,

Thanks! May I ask why you suggest hooking relay X/X up to aquastat T/T instead of connecting X/X to the aquastat ZC/ZR (with a jumper to the relay's ZC) as shown in the PDFs?

Paul48

The 8124 lo-limit has the ability to shut the circ off on a call for heat if the boiler temperature gets too low. This prevents return temperatures from getting too low and the boiler condensing. This would be an issue if you had a high volume system, and you don't. Wire it as Hatterasguy says.

Bob Bona_4

Might want to go with the SR506, so a future indirect water heater can be wired in with priority. Plus a spare zone.

ForTheGlory

Thanks everyone! It seems like I only have low limit protection on one zone currently, anyway.

Is there a functional difference between hooking the SR50x to aquastat T/T versus ZC/ZR?

I like the idea of doing an SR506 for future proofing. However, I am hoping that in the next few years my street will get gas and I can replace the oil boiler with a gas one. Am I correct that I will be able to use the SR50x with a gas boiler as well?

Paul48

Read the description of operation for the 2 different wiring options. http://www.taco-hvac.com/uploads/FileLibrary/SR504(102-084).pdf

For some reason it won't apply the link correctly. Copy and paste the whole address in the address line of your browser.

ForTheGlory

Thanks, I had looked at that before (I think I even linked it earlier) but discarded the diagram on the left because it said cold start.

Isn't the description on the right describing low limit protection? Except it says the boiler won't start until it is above the low limit. If the boiler isn't above the low limit, how can it get above the low limit without the boiler starting?

Paul48

@Joe Mattiello

Perhaps this will bring some assistance from Taco. I don't have the answer for that question.

ForTheGlory

Yep, I am going to call them tomorrow.

Bob Bona_4

Depends on what kind of gas boiler you get. The wall hungs generally have a built in circuit for DHW pump/priority. The stone age basic floor models generally do not. So, depending, you can be good with the 504, or would want the 506. For the minimal extra cost, why not cover yourself.

rick in Alaska

I am wondering why there is a single t-stat wired to the aquastat along with one of the circulators. Is there a possibility that the tstat is a master house stat, sort of like wwsd, and is maybe even running a primary loop?
Would love to see pictures of the boiler piping and the circulator placement.
Would make a difference on how things are wired.

Rick

ForTheGlory

rick, attached is a picture of the circulators. The one on the right is the one connected to the aquastat. Is there anything specific you would like to see about the piping? Also, what is wwsd? Thanks!

ForTheGlory

> @Paul48 said:
> OK......It doesn't affect which SR you choose, but you need to know if your boiler has a low water cut-off. It's a safety device that shuts the burner down if the boiler leaks and prevents a dry fire. Notice on the left of the wiring diagram.You want to make sure it doesn't wind up getting defeated by your new wiring(if you have one). Just make sure you follow the wiring completely.

Paul,

I looked at my boiler and I don't think I have a low water cutoff. There is a box with a switch and a fuse in it, and that outputs power directly to both the relays and the aquastat. Does this sound right?

Paul48

There's many boilers still out there that don't have them. Cross that bridge when you replace the boiler. That would be your service switch. The relays get disconnected and you power up the SR there, just like it shows.

ForTheGlory

Thanks Hatterasguy. I didn't mean to give the impression I didn't want to buy an SR506. I am actually planning on getting an SR506. I can't leave one of the zones on the L8124 since it doesn't have a common, and I am replacing the thermostats with ecobee3 units that require a common.